Field of the Invention
The invention relates to, in some aspects, systems and methods to remove materials of interest, including blood clots, from a body region, including but not limited to the circulatory system for the treatment of pulmonary embolism (PE), deep vein thrombosis (DVT), cerebrovascular embolism, and other vascular occlusions.
Description of the Related Art
It is understood that undesirable materials such as blood clots (which could be referred to as thrombi, thromboemboli, or emboli herein) in the blood vessels may partially or completely occlude blood vessels in areas of the coronary, cerebrovascular, pulmonary, peripheral venous, and peripheral arterial circulation resulting in myocardial infarction, stroke, pulmonary embolism, deep vein thrombosis, and infarction of an extremity respectively.
Various therapies and devices are known to either dissolve, debulk and/or aspirate the thromboemboli. For instance, anticoagulant agents such as heparin and warfarin help stabilize blood clots and prevent further forming of clots while thrombolytic agents such as urokinase, streptokinase, and tPA assist in dissolving blood clots. These agents can be delivered via systemic infusion or catheter-based infusion to the intended location. While thrombolytic agents can be effective in dissolving blood clots, they require a long time duration in order for the agents to dissolve the blood clots; thus patients may need to remain in the hospital intensive care unit (ICU) during thrombolytic infusion. Relatively long lengths of stay can increase healthcare costs significantly. A major limitation for these thrombolytic agents is that they can potentially cause intracranial, gastrointestinal, retroperitoneal, and pericardial bleeding, among other sites, which can be often life-threatening and cause significant morbidity and mortality risks.
Mechanical debulking and/or aspiration devices can be used to remove the obstruction. These mechanical techniques can either macerate, aspirate, or a combination thereof in order to remove the blood clots. An advantage of mechanical therapy is that it can remove thrombus directly from the blockage area and immediately eliminates the obstruction and may be superior to thrombolytic agents in some cases. However, current mechanical therapies have some major limitations. There is minimal to no flow during the procedure thus there is little time before patients may become hemodynamically instable. The debris removed from mechanical treatment can travel distally creating additional embolization. The small size devices are unable to remove large amount of blood clots in short time periods thus patients may become hemodynamically instable.
Catheter-based removal of blood clots from larger blood vessels (e.g., pulmonary arteries) have had limited success compared to smaller blood vessels (e.g., coronary arteries). Catheter pulmonary embolectomy is where pulmonary emboli are removed percutaneously using several techniques. Fragmentation thrombectomy breaks blood clots into smaller pieces, most of which travel further downstream, resulting in distal embolization. It is sometimes used in combination with thrombolytics. With the rheolytic thrombectomy, high velocity saline jets create a Venturi effect and draw the fragments of the clot into the catheter. This method poses risk of hemolysis. Finally the aspiration techniques draw the clot into a catheter via suction. All of these techniques rely on the catheter used to remove the clots from blood vessels. The users use small catheters to remove or break up large amounts of blood clot. This procedure is therefore time-consuming and inefficient. Once the blood clots are broken into small pieces, the debris can migrate distally and create unwanted emboli. Rheolytic therapy poses the risk of hemolysis. Additionally, the ability to suction is limited due the small catheter size suctioning large emboli. These limitations cause in some cases unnecessary duress to the user and risk to the patient.
Catheter-based removal of blood clots in general also has a major limitation when distal working space within a body lumen is limited. Conventional devices may require full axial and/or radial deployment and expansion to be functional, and as such flexibility to use such devices for a variety of clinical situations involving differing clot or other material sizes to be removed can be very limited. Therefore, conditions where there is limited distal space of blood vessels can render these conventional devices ineffective.
It is evident that all of the therapeutic options available to patients with blood clots or other undesirable material in blood vessels and other body lumens have limitations. Anticoagulation only limits propagation of clots but does not actively remove it. Thrombolytic therapy poses a risk of major bleeding. Catheter embolectomy is not effective to manage removal of material in large vessels. Additionally, these devices require distal space to fully deploy to be functional thus ineffective in tight distal spaces. Surgical embolectomy can be highly effective but highly invasive, and has a high rate of morbidity and mortality. There is a need for a direct mechanical treatment that is as or more effective as surgical embolectomy removing large blood clots but can be performed using endovascular techniques and restore immediate blood flow, and cause a lower incidence of complications.